A wide variety of elongate medical devices such as guidewires have been developed for use in conjunction with devices such as catheters to facilitate navigation through the anatomy of a patient. Guidewires can be used to access and navigate to a desired treatment site within the anatomy of a patient. Guidewires are often used as a guide for other devices that can be fed over the guidewire to the treatment site. Guidewires sometimes include a wider diameter proximal portion that is designed for relatively greater stiffness to enhance pushability and torqueability, and a distal portion that is designed for relatively greater lateral flexibility to enhance trackability and steerability. However, in at least some cases, the wider outer diameter proximal portion of the wire, which provides the desired, or even required stiffness characteristics for the particular procedure being performed, can interfere with the guidewires ability to function as guide for other devices. The larger outer diameter of the proximal portion may interfere with the feeding of some other devices over the wire. As such, during some procedures, it is often necessary to exchange one wire having the desired stiffness characteristics for another wire having the desired diameter for use as a guide for a particular device. Such exchanges are often undesirable. A number of different guidewire structures and assemblies are known, each having certain advantages and disadvantages. However, there is an ongoing need to provide alternative guidewire structures and assemblies.